I tried an dacorator event but for some reason it will not work and replace the flowers with my block, also i tried to only replace the flowers in one biome, here is my little event:

 

 

@SubscribeEvent
    public void plants (Decorate e) {
        if(e.getType() == Decorate.EventType.FLOWERS&&e.getWorld().getBiome(e.getPlacementPos()) == modbiome.WASTELAND) {
            e.getWorld().setBlockState(e.getPlacementPos(), modblocks.JUNK_BLOCK.getDefaultState());
        }
    }

Post all of your code.

Please refer to this image to setup up your event subscribers appropriately.

package com.Schleimtime.Wasteland.event;

import com.Schleimtime.Wasteland.init.modbiome;
import com.Schleimtime.Wasteland.init.modblocks;

import net.minecraftforge.event.terraingen.DecorateBiomeEvent.Decorate;
import net.minecraftforge.event.terraingen.OreGenEvent;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.Mod.EventBusSubscriber;
import net.minecraftforge.fml.common.Mod.EventHandler;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;

 

@Mod.EventBusSubscriber(modid = "wa")
public class destroyed {
    
    @SubscribeEvent
    static void plants (Decorate e) {
        if(e.getType() == Decorate.EventType.FLOWERS&&e.getWorld().getBiome(e.getPlacementPos()) == modbiome.WASTELAND) {
            e.getWorld().setBlockState(e.getPlacementPos(), modblocks.JUNK_BLOCK.getDefaultState());
        }
    }

 

 

package com.Schleimtime.Wasteland;

import com.Schleimtime.Wasteland.event.destroyed;
import com.Schleimtime.Wasteland.init.modbiome;
import com.Schleimtime.Wasteland.proxy.commonproxy;
import com.Schleimtime.Wasteland.util.reference;
import com.Schleimtime.Wasteland.world.types.worldtypewasteland;

import net.minecraft.world.WorldType;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.Mod.EventHandler;
import net.minecraftforge.fml.common.Mod.Instance;
import net.minecraftforge.fml.common.SidedProxy;
import net.minecraftforge.fml.common.event.FMLInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPostInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;

@Mod(modid = reference.MOD_ID, name = reference.Name, version = reference.Version)
public class Main {

    @Instance
    public static Main instance;
    
    @SidedProxy(clientSide = reference.CLIENT_PROXY_CLASS, serverSide = reference.COMMON_PROXY_CLASS)
    public static commonproxy proxy;
    
    @EventHandler
    public static void PreInit(FMLPreInitializationEvent e) {
        modbiome.registerBiomes();
    }
    @EventHandler
    public static void Init(FMLInitializationEvent e) {
    }
    @EventHandler
    public static void PostInit(FMLPostInitializationEvent e) {
        MinecraftForge.EVENT_BUS.register(destroyed.class);
        WorldType WASTELAND = new worldtypewasteland();
    }
}

 

i tried to make it like the picture and tried out the static one but thats also not working, i treid an event that will send a message on block break and that worked for some reason